In a world where everyone is born with triangular heads that grow more complex with age, a boy struggles to belong. After failing to connect with peers through a paper crane, he learns from his father to suppress his "childish" nature. He eventually succeeds in reshaping his head to fit societal norms, only to lose his sense of wonder. Years later, as a distant, practical father, he overlooks his son’s longing for attention. The protagonist’s inner child remains buried until he finds a drawing in his briefcase: a sketch of himself and his son with matching triangular heads. In a moment of clarity at the airport, he folds the drawing into a crane, reuniting with his younger self. Rushing home to embrace his son, a faint triangular aura flickers around his head, a sign that his true essence, though hidden, was never truly lost.